Money time in France’s current presidential election won’t come before the May 6 run-off between probable mainstream finalists, incumbent conservative Nicolas Sarkozy and Socialist François Hollande. For now, though, that all-important showdown is being overshadowed by two candidates from opposing political extremes whose long-shot bids—and growing support—are stealing much of the campaigning thunder. Though it’s quite unlikely either hard-left champion Jean-Luc Mélenchon, or National Front leader Marine Le Pen will rise fast enough to challenge Sarkozy or Hollande for the second of two face-off slots, their increasing success indicates the next French president will need considerable support from one of France’s swelling electoral extremes to win.

Jaws across France dropped April 1 when a poll showed Front of the Left candidate Mélenchon capturing 15% of first round voter intent, inching out Le Pen’s 13.5% stake for third place behind Hollande and Sarkozy. That score more than doubled the 6.5% support Mélenchon enjoyed as recently as mid-January. It was fueled by an increasing flow of voters—primarily from Hollande’s center-left camp—joining Mélenchon’s mix of Communist, anti-capitalist, and environmentalist backers. Averaged out, the myriad surveys in France’s presidential race reflect Le Pen maintaining her third position in projected April 22 voting of about 16% over Mélenchon’s 14.5%, well behind Hollande and Sarkozy’s virtual tie of about 28%. But in addition to their possible kingmaker roles in endorsing second round finalists, both Mélenchon and Le Pen have become significant and opposing conduits of French voter demands on the next French president.

Le Pen’s hopes of replicating her father’s 2002 achievement of qualifying for the run-off round against a mainstream rival have faded as her projected scores have slumped from a high of nearly 19% in January. That erosion has come in part through Sarkozy’s decision to adopt similar hardline positions on immigration, security, and economic protection to lure National Front voters to his cause—a gambit that proved essential to his 2007 triumph. He’s also stepped up high profile anti-terror operations in the wake of the Toulouse killing spree by Mohammed Merah that claimed seven victims.

Those maneuvers forced Le Pen to harden her anti-European, Islamophobic, immigration-bashing rhetoric to defend her far-right turf and voter base. She’s also begun ravaging Sarkozy as a scheming poacher of her traditional electorate’s concerns. Sarkozy’s encroachment has similarly provoked Le Pen’s high volume claims of being the only insurgent candidate prepared to bring down France’s cosseted, compromised political class. That anti-establishment push has earned Le Pen a 26% voter score among people aged 18 to 24 –a demographic facing unemployment rates of nearly 25%, and often shut out of active French life. Hollande ranks second among young voters with 25% support, followed by Sarkozy and Mélenchon with 17% and 16% respectively.

Despite her growing popularity and recent anti-Sarkozy counter-offensive, Le Pen’s campaign is now being eclipsed by Mélenchon’s dramatic advance. A former Socialist who has re-cast himself as an anti-globalization champion of France’s shrunken hard left, Mélenchon, 60, is drawing alienated progressives and even disgruntled working class conservatives to his original base of Communist Party backers. In addition to his emphatically leftist program—calling for 20% rise in minimum wage, major restrictions on company lay off abilities, and heavy taxation of the rich and financial markets—Mélenchon is also gaining attention with his witheringly satirical attacks on rival candidates. A quasi-revolutionary zeal, stark positions, and razor-sharp tongue have Mélenchon looking something like the Ann Coulter of France’s hard left.

Mélenchon’s aggressive campaigning and resulting polling lift has come largely at Hollande’s expense. In the past, Mélenchon has denigrated his former Socialist Party colleague as an inept “pedal boat captain,” and savaged Hollande’s program as (gasp!) bourgeois centrism. That’s worked like a charm—indeed, so well that Mélenchon has had to backtrack amid cheers from conservatives at Hollande’s dip in first round support. Now Mélenchon is re-directing fire at Sarkozy—who he vilifies as a heartless, corrupt minion of the wealthy. He’s also lambasting Le Pen’s populist appeal at the other end of France’s political spectrum. The multiple clashes have made the battle between Mélenchon and Le Pen for third place in April 22 voting as brutal as the fight for first place between Hollande and Sarkozy is.

But what does it all mean for the May 6 final? Most recent polls show Hollande beating Sarkozy by 8% to 10%. But with over 30% of voters saying they’re still undecided or could change their minds, the final result is expected to be far tighter. The outcome will lie in large part on how ballots benefiting the extremes in the first round are redistributed in the second. Unlike Le Pen—who has said she will not instruct her electorate to back Sarkozy May 6—Mélenchon has indicated he’ll urge his backers to vote out Sarkozy (without necessarily endorsing Hollande) in the run-off. Polls now suggest Hollande will indeed inherit at least 80% of all votes cast for other leftist candidates in the first round. By contrast, 51% of people saying they’ll vote for Le Pen April 22 are undecided about who’ll they’ll back in the second round. Just over 30% Le Pen backers say they’ll abstain May 6. Still too many “ifs” remain to know who will prevail.

“In order to win, Sarkozy must find a way to get even more extreme-right voters casting ballots for him May 6 than Hollande can attract from the Mélenchon camp,” says Dénis Muzet, president of the Paris-based Institut Médiascopie public opinion research group. “But because whichever candidate wins will do so with significant support from one of the two extremes, he’ll have a very hard time responding to those demands once the election is over. As a result, it won’t take long before victory cheers give way to angry cries of betrayal from the extremes. Ironically, those fringes are now too large electorally to ignore, but too excessive in their demands to base policy on.”